title: Rapid recruitment of BRCA1 to DNA double-strand breaks is dependent on its association with Ku80.
abstract: BRCA1 is the first susceptibility gene to be linked to breast and ovarian cancers. Although mounting evidence has indicated that BRCA1 participates in DNA double-strand break (DSB) repair pathways, its precise mechanism is still unclear. Here, we analyzed the in situ response of BRCA1 at DSBs produced by laser microirradiation. The amino (N)- and carboxyl (C)-terminal fragments of BRCA1 accumulated independently at DSBs with distinct kinetics. The N-terminal BRCA1 fragment accumulated immediately after laser irradiation at DSBs and dissociated rapidly. In contrast, the C-terminal fragment of BRCA1 accumulated more slowly at DSBs but remained at the sites. Interestingly, rapid accumulation of the BRCA1 N terminus, but not the C terminus, at DSBs depended on Ku80, which functions in the nonhomologous end-joining (NHEJ) pathway, independently of BARD1, which binds to the N terminus of BRCA1. Two small regions in the N terminus of BRCA1 independently accumulated at DSBs and interacted with Ku80. Missense mutations found within the N terminus of BRCA1 in cancers significantly changed the kinetics of its accumulation at DSBs. A P142H mutant failed to associate with Ku80 and restore resistance to irradiation in BRCA1-deficient cells. These might provide a molecular basis of the involvement of BRCA1 in the NHEJ pathway of the DSB repair process.
authors.affiliation: Department of Clinical Oncology, Tohoku University, 4-1 Seiryomachi Aoba-ku, Sendai 980-8575, Japan.
authors.forename: Leizhen
authors.initials: L
authors.lastname: Wei
authors.forename: Li
authors.initials: L
authors.lastname: Lan
authors.forename: Zehui
authors.initials: Z
authors.lastname: Hong
authors.forename: Akira
authors.initials: A
authors.lastname: Yasui
authors.forename: Chikashi
authors.initials: C
authors.lastname: Ishioka
authors.forename: Natsuko
authors.initials: N
authors.lastname: Chiba
mesh_terms: D034961:Antigens, Nuclear / Q000235:genetics / Q000378:metabolism*; D019313:BRCA1 Protein / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D004247:DNA / Q000528:radiation effects*; D053903:DNA Breaks, Double-Stranded; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D006657:Histones / Q000235:genetics / Q000378:metabolism; D006801:Humans; D000072200:Ku Autoantigen; D007834:Lasers; D020125:Mutation, Missense; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism
chemical_list: D034961:Antigens, Nuclear; D019313:BRCA1 Protein; D004268:DNA-Binding Proteins; C468783:H2AX protein, human; D006657:Histones; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D025521:Tumor Suppressor Proteins; D004247:DNA; C102449:BARD1 protein, human; D044767:Ubiquitin-Protein Ligases; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen